The present invention relates in general to a fuel-water filter dehydrator and more particularly to such a filter dehydrator useful for removing free water from aviation fuel.
It is critically important that aviation fuel for today's high-performance aircraft engines be of high quality. Typical aircraft fueling systems include efficient filtration and water separation equipment. However, it is desirable that a system include means which will prevent unacceptable fuel from passing into the aircraft.
Many fuel water separator systems include some type of coalescer and filter separator elements which retain the solid contaminants contained in the fuel flowing through the system and are effective to coalesce and remove the water content therein. In removing the solid contaminants of the transient fuel, the elements gradually offer increased resistence to the flow of fuel until the attained pressure drop across the element becomes greater than the system pressure can attain. If the element is not replaced before this occurrence, the element will malfunction and discharge into the aircraft fuel tanks a large quantity of contaminants, both solid and water. Also, it has been found that in certain circumstances the fuel being passed through the fuel water separators may contain surfactants and the like, causing the coalescer elements to be inoperative or ineffective in coalescing and removing the water content of fuel.
As a result of the aforementioned problems, water sensitive flow monitors have been designed to block the flow of fuel containing an unacceptable concentration of free water therein. Military specification MIL-M-81380B(AS) dated Sept. 19, 1975 has even been written to specify the effectiveness of such flow monitors.
U.S. Pat. Nos. 3,528,546 to R. W. McPherson and 3,528,547 to R. E. Adams et al., both assigned to the assignee of the present invention, disclose water sensitive flow monitors containing respectively a granular bentonite material or an algin material provided in such a water sensitive flow monitor. U.S. Pat. No. 3,572,510 to S. J. Lyda discloses a monitor filter employing a polyethylene oxide between a fiberglass filter tube and a cellulosic fiber confining filter. It has been disclosed to include in a monitor of this general configuration a fail-safe mechanism which automatically shuts off the flow of liquid hydrocarbon fuel. U.S. Pat. No. 3,710,822 to S. J. Lyda discloses a shut-off valve inside the monitor of the construction of the above referenced Lyda patent. Lyda U.S. Pat. No. 3,710,822 also makes reference to other shut-off devices, such as a compressed coil spring held under tension by a strip of hydrophilic paper or a plastic ball acting in conjunction with an aluminum ring.
One such shut-off device is described in U.S. Pat. No. 3,406,827 to G. J. Topol et al. and is marketed by Keene Corporation under the name Petroguard. This product includes a fiberglass layer surrounding a phenol formaldehyde resin impregnated cellulosic material. The monitor element has a reduced thickness near the hydrophilic paper strip to allow passage of some water to trigger the unit as a fuse. Necessarily, at least some water must pass through the filter element into the outlet in order for the unit to operate as a fuse monitor.
It is the object of the present invention to provide a new improved filter dehydrator which will block the flow of fuel containing an unacceptable concentration of water therein and remove water from fuel.
Broadly stated, the present invention, to be described in greater detail below, is directed to a filter dehydrator for transient hydrocarbon fluid comprising an inlet and an outlet, a mass of water absorptive cellulosic fibers disposed between the inlet and the outlet and media disposed upstream of said water absorptive mass for removing solid particles that would block the active surface of the mass and disperse water droplets in the hydrocarbon fluid.
In accordance with a preferred embodiment of the present invention the water absorptive cellulosic fibers comprise a water-insoluble cross-linked carboxymethyl cellulose fiber. Such a material is described in U.S. Pat. No. 3,589,364 to W. L. Dean et al. which describes the method of manufacture of such material and the absorptive characteristics of the material. It is not certain whether such material has adsorptive qualities as well, so the term "absorptive" is used herein to mean the qualities of a material made as described in that patent.
A feature and advantage of the present invention lies in the fact that apparatus or elements constructed in accordance with this invention can serve the dual functions of a filter and a dehydrator. The elements can serve as both the primary filter, as well as a dehydrator in those instances where another filter system is unavailable and can serve as a dehydrator in situations where a conventional prior art type filter is already provided.
In accordance with another aspect of the present invention a fiberglass material serves as the media upstream of said water absorptive mass for both filtering solid particles that would block the active surface of the mass and disperse water droplets in the fluids. These two functions could be performed separately by other materials, but can be performed simultaneously by appropriate fiberglass.
It has been discovered that fiberglass with average fiber diameters of substantially 0.00005 inches and a density of substantially 10 pounds per cubic foot will perform both of these functions with water-insoluble cross-linked carboxymethyl cellulosic material in this filter dehydrator.
The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of certain preferred embodiments of the invention, taken in conjunction with the accompanying drawings wherein the same reference number refers to the same or similar elements in each of the several views.